Field of the Invention
The present invention relates to an integrated transformer having first and second coils that are electrically insulated from one another. The first and second coils have spiral courses and the first coil has a rectangular cross section.
A transformer configuration of this type is described for example in Published British Patent Application GB 2173956 and in Published German Patent Application DE 101 00 282.3.
Such planar transformer configurations are used in signal transmission if it is necessary to feed a signal generated by one circuit configuration to a further circuit configuration while electrically isolating the circuit generating the signal from the circuit that processes the signal further.
In this case, the two coils are arranged such that they are electrically insulated from one another and adjacent to one another, in order to ensure an inductive coupling of the two coils. Usually, a core is not used in planar integrated transformers, for which reason these transformers are also referred to as coreless transformers.
What is critical for the transmission properties of such a transformer is the time constant τ=L/R of the primary winding, which is given by the quotient of the inductance L and the winding resistance R. The transmission effectiveness improves as the time constant increases.